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[Xen-ia64-devel] Re: [Xen-devel] Porting PV-on-HVM for ia64 platform

I (Doi.Tsunehisa) said:
> You (Keir.Fraser) said:
>> On 26/8/06 6:50 am, "Tsunehisa Doi" <Doi.Tsunehisa@xxxxxxxxxxxxxx> wrote:
>>> - In x86 code, original shared_info page is used after pv-on-hvm
>>> setup with remapping feature in arch depend HYPERVISOR_memory_op.
>>> But, we can't implement same feature for IPF, thus we select to
>>> implement with this method.
>> Why is that? It's a change to the P2M map -- it's not an x86-specific
>> operation.
>   We had tried to implement it with the same method as x86 code, but we
> couldn't success to implement it. If we will refere to implementation of
> grant table operation, we may be able to success to implement it, but
> it's not easy for us, I think.

  I'll try to describe the reasoon which I think about.

  In IPF, V2P address translation uses TR, TC and VHPT. VHPT is like page
table in x86 platform, and TC is like TLB in it exept for direct handling
posibility. But TR is specific for IPF. TR is controled directly with MM,
its entry does not be deleted by hardware if MM does not control it.

  In additionaly, TR, TC and VHPT can use flexible page size for each entry.
Thus normal linux kernel uses a TR entry for kernel virtual space. So, in HVM
domain on IPF, it is difficult to change a part of P2M map of kernel virtual
space without MM modification.

-- Tsunehisa Doi

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